Referring to FIG. 1, a pet cage 1 of the prior art comprises six meshed boards 10, being mutually connected by point welding spots 11 to form a rectangular pet cage 1. One of the meshed boards 10 is provided with a door 12 for the entrance of a pet. Each of the four corners of the cage is further provided with a leg 13. However, the meshed boards 10 of the pet cage of the prior art are fixed by welding and therefore cannot be disassembled or folded, resulting in inconvenience of storage and carrying. Further, the connection of the meshed boards 10 is usually by point welding, which will be eroded after a period of time and thus not durable. It is further disadvantage that the display of many pet cages in a compact space requires piling up of the cages. The connection of an upper cage and a lower cage is usually done by inserting the legs of the upper into the top side of the lower, forming a structure of low stability against external disturbances. The pets kept inside the cages would be easily frightened.